This application relates generally to optical routing and more specifically to microelectromechanical systems for routing optical signals.
The Internet and data communications are causing an explosion in the global demand for bandwidth. Fiber optic telecommunications systems are currently deploying a relatively new technology called dense wavelength division multiplexing (DWDM) to expand the capacity of new and existing optical fiber systems to help satisfy this demand. In DWDM, multiple wavelengths of light simultaneously transport information through a single optical fiber. Each wavelength operates as an individual channel carrying a stream of data. The carrying capacity of a fiber is multiplied by the number of DWDM channels used. Today DWDM systems employing up to 80 channels are available from multiple manufacturers, with more promised in the future.
In all telecommunication networks, there is the need to connect individual channels (or circuits) to individual destination points, such as an end customer or to another network. Systems that perform these functions are called cross-connects. Additionally, there is the need to add or drop particular channels at an intermediate point. Systems that perform these functions are called add-drop multiplexers (ADMs). All of these networking functions are currently performed by electronicsxe2x80x94typically an electronic SONET/SDH system. However SONET/SDH systems are designed to process only a single optical channel. Multi-wavelength wavelength systems would require multiple SONET/SDH systems operating in parallel to process the many optical channels. This makes it difficult and expensive to scale DWDM networks using SONET/SDH technology.
The alternative is an all-optical network. Optical networks designed to operate at the wavelength level are commonly called xe2x80x9cwavelength routing networksxe2x80x9d or xe2x80x9coptical transport networksxe2x80x9d (OTN). In a wavelength routing network, the individual wavelengths in a DWDM fiber must be manageable. New types of photonic network elements operating at the wavelength level are required to perform the cross-connect, ADM and other network switching functions. Two of the primary functions are optical add-drop multiplexers (OADM) and wavelength-selective cross-connects (WSXC).
In order to perform wavelength routing functions optically today, the light stream must first be de-multiplexed or filtered into its many individual wavelengths, each on an individual optical fiber. Then each individual wavelength must be directed toward its target fiber using a large array of optical switches commonly called an optical cross-connect (OXC). Finally, all of the wavelengths must be re-multiplexed before continuing on through the destination fiber. This compound process is complex, very expensive, decreases system reliability and complicates system management. The OXC in particular is a technical challenge. A typical 40-80-channel DWDM system will require thousands of switches to fully cross-connect all the wavelengths. Opto-mechanical switches, which offer acceptable optical specifications, are too big, expensive and unreliable for widespread deployment. New integrated solid-state technologies based on new materials are being researched, but are still far from commercial application.
Consequently, the industry is aggressively searching for an all-optical wavelength routing solution that enables cost-effective and reliable implementation of high-wavelength-count systems.
Embodiments of the invention provide a microstructure for steering light that provides enhanced flexibility. The microstructure may be configured to function as an optical switch for directing an optical signal from a single input port to one of at least three output ports. Such configurations may be adapted for use in a wavelength router. Alternatively, the flexibility of the microstructure may be used to achieve improved alignment so that the light-steering efficiency is improved.
In one embodiment, a microstructure for steering light is provided. A pivot member is connected with a structural film and supports a base that includes a reflective coating. A first fixed rotational actuator is connected with the structural film and is configured to rotate the base on the pivot member upon actuation. A first movable hard stop is connected with the structural film. The first movable hard stop is configured such that in each of a plurality of its positions, the base assumes one of a first plurality of tilt positions upon actuation of the first fixed rotational actuator.
In some embodiments, a second fixed rotational actuator is also connected with the structural film and is configured to rotate the base on the pivot member upon actuation. A second movable hard stop is connected with the structural film. Each of a plurality of positions of the second movable hard stop causes the base to assume one of a second plurality of tilt positions upon actuation of the second fixed rotational actuator. The first and second movable hard stops may have their positions correlated with each other, such as by connecting them. In some embodiments, the movable hard stops may be linearly actuated.
In certain embodiments, the movable hard stops comprise a plurality of discrete levels, each of which corresponds with one of the plurality of positions of that hard stop to define one of the plurality of tilt positions. Where two movable hard stops are provided, they may have the same number of discrete levels.
In some embodiments, the pivot member comprises a torsion beam. In other embodiments, the pivot member comprises a cantilever. The reflective coating may comprise gold.